<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>

        /* div{width: 100px; height: 100px; background-color: red} */
        div{width: 50%; height: 200px; background-color: red}
        span{background-color: blue}
    </style>
</head>
<body>
    <div>这是一个块</div>
    <div>又是一个块</div>
    <span>这是一个内联</span>
</body>
</html>